1. Field of the Invention
This invention pertains generally to precision farming methods, and more particularly to ultra-precise (i.e., centimeter accuracy), Global Positioning System (GPS) based mapping of seeds and vegetation while dispensed from a planter for site-specific cultivation and plant specific chemical application.
2. Description of the Background Art
Successful agricultural enterprises seek to optimize crop production while minimizing the input costs of applying herbicides and fertilizers and other activities thereby maximizing the profits realized from a particular crop. It is common practice for the typical farmer to apply pesticides or fertilizers uniformly throughout the field even though less than 50% of land area is covered by the target foliage. Precision farming techniques such as yield monitoring, variable rate applications, crop and soil property sensing etc. can allow a reduction in the application of chemical pesticides and fertilizers by delivering the chemical to the crop plant rather than the entire field. The annual application of pesticides and fertilizers by agriculturalists in the United States alone is substantial. For example in 1989, over 800 million pounds of pesticides were used in US agriculture. Accordingly, targeted spray can lead to a huge reduction of chemical input into US agriculture. This approach not only reduces the cost of chemicals, but also reduces the pesticide load on the environment, particularly on ground water and streams. Such precision techniques have had limited success because they are often man-power intensive to assure accuracy.
One of the key elements that aided the development of precision farming techniques is the ability to “accurately” determine the locations within a field using GPS technology. Sub-meter accuracy offered by early GPS systems that utilized differential corrections (DGPS), has been satisfactory for many precision farming applications where sub-meter accuracy is acceptable.
The recent development of real-time kinematics (RTK) based GPS systems have made it possible to determine field positions with an accuracy of 1 centimeter. The application of this technology to agriculture can have tremendous economic and environmental benefits. The centimeter accuracy of the RTK based GPS technology allows the movement from site-specific precision farming with sub-meter accuracy to plant-specific ultra-precision farming with centimeter accuracy.
Many different types of autonomous systems have been attempted for use with agricultural vehicles. One system used radio frequency to guide a tractor with an accuracy of less than 5 centimeters. Another utilized a laser guidance system to achieve an accuracy of less than 6 millimeters. Image analysis systems using a video camera have also been developed, some reporting accuracy of around 7 millimeters at low weed loads and 12 millimeters at high weed loads with permitted speeds up to 16 kilometers per hour. Other imaging based systems utilize a color vision system to discriminate between plants and weeds to allow differential spraying. However, since optical discrimination between plants and weeds using image analysis to extract relevant features is computationally intensive, these systems must employ very low ground speed. Mechanical systems have also been developed using a leader cable system for reliable tractor guidance or implemented a mechanical contact type guidance system for use in green houses. Other systems use a combination of ultrasonic and dead reckoning to guide a tractor. Finally, other precision farming systems have used RTK GPS for vehicle guidance because of its technical superiority and economic advantages compared to all other systems.
Accordingly, a need exists for accurate and inexpensive precision farming techniques that can efficiently identify the location of seeds and plants within a field for selective application of pesticides and fertilizers and tilling without causing operator fatigue or having large man-power requirements. The present invention satisfies that need, as well as others, and generally overcomes the deficiencies found in existing equipment.